Feed adjustment device



INVENTOR. RAYMOND C. PALMER BY 7)MMQCW lllllllllliggl p wllllll R. C. PALMER FEED ADJUSTMENT DEVICE Filed Aug. 25, 1949 Dec. 26, 1950 ATTORN EYS FIG. 4

Patented Dec. 26, 1950 UNITED STATES PATENT OFFICE 2,535,228 Fun f) A iips'rmnn'r mutter Raymond o. ialmer, Chicago; 111'. ApplicatioiiAugust 25, 1949; Serial No. 112,355

This invention relates to adjustment devices and more particularly to adjustment devices'of a type particularly well adapted for adjustingthe feed mechanism of machine too-ls and the like.

In adjusting the feed of machine tools to thereby position the position of the cutting tools and the like, it is important for the performance of accurate machining that such adjustments be made accurately, and that, when the accurate adjustments are once made, they be maintained during the subsequent operation ofthe machine. It is a primary object of my invention to enable such accurate adjustments, and such maintenance of accurate adjustments, to be effected Various types of adjustment devices have been heretofore used or resorted to in adjusting the feed of different machine toolss uc h as, for example in making" vertical adjustments of the spindle in a milling machine, or the' like. How'- ever, one of the major problems heretofore exfperienced in the art has beento eliminate backlash in the adjusting device which backlash, as is well'know'n to those skilled in the art,"is seriously detrimental to the accurate operation of ma chine tools.

An important object of my invention is to eliminate backlash in the feed ad"usti'n'ent of machine tools such as, for example, milling machines and the like. V

In feed adjusting devices of the general'typ'e' towhich my invention applies, adjustment of the feed member of the machine tool is effected through a driving member engaged with a driven member. As is well known to t ose skilled in the art, when two members are operating in erigage-' to enable the relative po ition o5 driven member and driving m mber: of such adevice to be adiusted in a novel and expeditious manner so as to compensate for thisnormal wear 1? nd maintain a close fitting engagement therebetween.

Normally, in machine tools of theltype hereto l. fore known in the art, adjustment of the feed of a machine. and the maint nance mm ad r; merit has been accomplishedby twolseparate mechanisms.

with the'use ofjone sex/ice, an afiterfthe a' us For example, it has f h'eretofore been common practice in the machine] toollart to adjust the position of thecutting toolfor thelike,

wise undesirablej during the finishing operations on a workpiece wherein a' seriesof relatively thin finishing cuts, or the like, may be su'cc's sively take'n, with the, cutting tool, being ad vanced very slightly between the successive cuts.

, It is anfobjectfloi myfinvention to provide a 'ieedadju'stment device which isope'rablej to adjusttheieed mechanism of tools, and tain the feed mechanism in such adjusted position, in a practical, and efficient manner. E A further object isgto afford a novel feed ad'- ius'tment' device which is automatically effective positively retain'the feed adjustment of a in nine: too1,' or the like, upon completion of; a

feed edjustingoperation or the device;'so that it i'sunnicessary for th'e operator to perform a separate? locking operation each, time that an at, ustment' of the feed of themachine' is made;

Yet another object of my invention is'to" a'fiford a feed adjustment devicejwhich is effective, to strong1yI.,Support.thefeed mechanism 'p'f alma chine tool adjusted thereby in a novel and ex'- p 'd usm j r..,,,.

.Q h l an her object ip the s n vention will be apparent from'the following. dek,

scription and claims and arejillustrated, in the accompanyingdrawings which, by way of illus iirti fi, s ow ap err emb d ent and t e,

principles thereoj and whatI now consider tobe the bestm'ode' in which I have cor'itje n iplatle'd applying those; principles. Other embodiments', of

he .in en an mbodyin th v sam Orem i caI h p'rineiples may be ufsed anid'structural chahgesj may be made as desired by those skilled artf without departing from the present, inven tion' and the purview oftheap'pended claims.

n t d a ings:

Ejig lis a sectio'na'l View ofaiedad," stment" 'e iilce embodying the principles or my, inven} tion, showing theflfeed adjustment device attached to a'ma'chinetool;

2'is a sectional view taken substantially aloiigjtbe' 11 2 2 in F g; 1; I

FigI'B is afjse'ctional View takensub ttantially along the line 3 53" in Fig. 2;

g; 41 a detail secncnai V ew taken new 5 is a detail sectional new,assistant tiallyal'oh'g'theline s -tin' Fig. 2';

Fig. 6 is a detail sectional view taken substantially along the line 65 in Fig.

Fig. 7 is a detail sectional view taken substan tially along the line l-? in Fig. 1; and

Fig. 8 is a detail sectional view somewhat similar to Fig. l but showing a modified form of my invention.

A typical embodiment of my invention is illustrated in Figs. 1 to 7, inclusive, of the drawings, wherein is shown a portion of a milling machine M embodying a cylindrical-shaped spindle S reciprocably mounted in a bore B in a housing H, a feed adjustment device D being mounted on the housing H for adjusting the position of the spindle S longitudinally in the bore B. The spindle S may be of any suitable form such as that shown in my co-pending application, Serial No. 25,765, filed May 7, 1948.

As is best seen in Fig. 1, the housing H comprises two side walls 2! and 22, two end walls 23 and 24, and an intermediate wall, or partition wall 26 extending between the side walls 2! and 22, the end wall 23 and the partition wall 26 forming arcuate extensions of portions of the side walls 2! and 22 to afford the cylindricalshaped bore B. The spindle S is reciprocable in a longitudinal direction in the bore B and is restrained from rotating therein by a key 3! secured to the side wall 22 by suitable means such as screws 33 and extending into a slot or keyway 35, Figs. 1 and '7, formed in the spindle S.

A feed rack 38, comprising a plurality of suitable tapered threads 39 is formed on one side of the spindle S, with the threads 59 spaced longitudinally therealong, and is disposed in alignment with a slot sl formed in the partition wall 26, the key 3i being effective to hold the spindle S against rotation in the bore B, as previously mentioned, to thereby maintain the rack 38 in alignment with the opening 49. 38 affords means engageable through the slot M by feeding mechanism on the feed adjustment device D, to thereby effect longitudinal movement of the spindle S in the bore B, during actuation of the feed adjustment device D, as will be presently discussed in greater detail.

The feed adjustment device D comprises two bearing blocks 55 and Figs. 2 and 3, mounted on the inner face of the end wall 24 of the housing H by suitable means such as welding. elongated bore 4? and extends through each of the bearing blocks 45 and 46, respectively, and each includes an enlarged end portion Ala and 48a and a reduced end portion 57b and 43b, respectively, the reduced end portions 41b and 48b being disposed in axial alignment with complementary openings 5! and 52, respectively, formed in the end wall 24 of the housing H in communication with the reduced end portions 41b and 48b of the openings ll and 48. The bearing blocks 55 and 46 are disposed in parallel relation to each other on the side wall 24 of the housing H and have elongated slots 54 and 55 extending therethrough, Figs. 3 and 5, in alignment with the longitudinal axis of the bearing blocks and 35 and the longitudinal openings 4'! and 48 therein, one end of the slots 5G and 55 and opening outwardly through the end portions of the bearing blocks and 45 in which the enlarged portions Ala and 58a. of the openings 41 and 43 are disposed, and the other end of the slots 54 and 55 terminating in spaced relation to the reduced portions 412) and 48b of the openings 41 and d3, respectively.

Two bearings 57 and 58 are slidably mounted The feed Tack teriorly of the housing H and affords means in the enlarged portions 41a and 48a of the openings 4? and 43 and have cylindrical-shaped openings SI and 62 extending transversely therethrough. When the slidable bearings 57 and 53 are mounted in operative position in the bearing blocks a5 and 46, the openings 6| and 62 in the slidable bearing are disposed in alignment with the slots 54 and 55 formed in the bearing blocks 45 and 45, and an elongated shaft 64 is snugly but rotatably journaled in the openings 6i and 62. The close fit between the shaft 54 and the slidable bearings 5'! and 53 should be carefully maintained so as to eliminate undesirable lateral movement of the shaft i l in the openings 6! and 52, as will be discussed presently.

A worm 66, Figs. 2 and 3, is mounted on the shaft 5 3 for rotation therewith, and has one face 5? engaged with the bearing block 45, Fig. 3. A hub member at projects from the other face of the worm 65, and a spiral gear H is mounted thereon for rotation with the Worm 55. The worm 56 is preferably mounted on the shaft 64 with a shrink fit, so as to be firmly connected thereto and rotatable therewith; and the spiral gear ii is preferably mounted on the hub 69 of the worm 58 with a similar fit so as to be rotatable therewith. However, as will be appreciated by those skilled in the art, other means such as, for example, pins or keys may be used, if desired, to efiect this positive connection between these three members.

A gear "i3, Figs. 1 and 3, which is fast to a shaft journaled in the partition walls 26 and 24, is engaged with the gear ll and is effective to rotate the latter and, therefore, the worm upon rotation of the shaft 15. One end of the shaft 75 extends outwardly through a boss '56 on the end wall 2:! of the housing H, and a crank it is mounted on the latter end of the shaft i5, ex-

whereby the shaft 15, and, therefore, the gears 73, H and may be rotated. If desired, suitable indicia I, Fig. 1, may be afforded on the crank Ti and the boss 76 to indicate the position of the crank Tl, as will be understood by those skilled in the art.

The bearing blocks 45 and 46 are so disposed on the end wall 2:! of the housing H that the shaft 64 and the worm 56 are disposed in parallel relation to the opening ll in the partition wall 26, and the feed rack 38 on the spindle S. The threads 81 on the worm 56 are complementary to and engageable with the threads 39 on the spindle S, and the bearing blocks 25 and 48 and the slidable bearings 5! and 53 are so disposed in the housing H that when the slidable bearings 5? and 58 are disposed in proper position in the bearing blocks 25 and 46, the threads 8! on the worm 66 are drivingly engaged with the threads as on the feed rack 88 of the spindle S.

As previously mentioned, the threads 39 are tapered threads, and the threads 8! are complementary thereto. For the purposes of my invention it is preferable that the threads 39 and 8! formed on the spindle S and the worm 66, respectively, be Acme threads, whereby, when the worm 66 is firmly engaged with the rack 38, the oppositely disposed tapered faces Ma and Nb of the threads 8! are firmly engaged with corresponding faces 39a and 39b of the threads 39 engaged by the threads SI to thereby afford a Wedging engagement between the threads 3| on the worm 66 and corresponding threads 39 on the rack 38 which is effective to hold the spindle 8- against longitudinal movement in either directionrelative to the worm 66.

It will be seenthat, with the spindle S and-v worm 66 relative to the housing H, the spindle S- is likewise held against longitudinal movement relative to the housing H. To efiect such positive longitudinal positioning of the worm 56 in the housing H I prefer to mount suitable spacers such as the spacer or shim 82 between the bearing block 55 and the spiral gear H, Figs. 2 and 3, to thereby press the opposite face of the worm 66 into snug, but not tightly binding, engagement withthe adjacent face of the bearing block 46. As wear occurs between the worm 66 and the bearing block 46-, or between the spiral gear H, the spacer 82, and the bearing block 45, heavier shims may be substituted for, or added to the shim 82 tothereby maintain a snug engagement between the bearing blocks 55 and i6 and the spiral gear'BZ and the worm 5-6 and thereby prevent undesired longitudinal movement of the worm 66a For'adjusting the position of the shaft 64 and, therefore; the worm 66 relative to the rack 36 on the spindle S. to thereby afford the aforementioned firm interengagement of the worm 66 with the rack 38; I aiiord means for effectively adjusting the position of the slidable bearings 51 and 58 in the bearing blocks t5 and 46. Thus, as is best seen in Figs. 2, 4, 5 and 6, screws 83 l and 84, having outwardly projecting heads, are threadedly engaged in the openings :ilb and 5! and the openings 48b and 52, respectively, and abut the outer ends of the slidable bearings 5'1 and 58; respectively. Thus, it will be seen that by turning the screws 83 and 8 in the proper direction; theslidable bearings 57 and 58 may be released for movement away from the spindle S, or may be forced inwardly by the screws 83 andBltoward' the spindle S. The slidable bear- 1';

i'ngs 5'1 and preferably fit snugly in the openings 47 and d3 so as to eliminate undesirable lateral movement of the b arings 5! and 53 relative to" the bearing blocks and 45. In addition, two set screws 85 and B1 are threaded into the bearing'blocks G5 and 46 and are engageable with the sides of slidable bearings 5iand 58, respectively; to thereby aiford means for effectively securing the slidable bearings 57 and 58 in the ad' justed positions determined by the positions of the-screws 83* and 84, the set screws 85 and 81 being effective to press the slidable bearings 5'! and 58 into binding engagement with the opposite side walls of t e o en ngs il and 48 to thereby insure that the slidable bearin s 51 and 58' will not mo e either lat ra ly or longitudinally in the openings 41 and 48. If for any reason, such' as; for example, if we r between the worm 66* and the rack 38' c use the int ren aeem -nt thereof to loo en omewhat, it subseo ently is 'desirable torewdu t the po ition of the worm 66 relative to the spindle S. this may be readilv accomplished by loos ning t e set screws 86 and 81, and. upon rotatin th adu t n screws 83 and: 84" in the rop r direction shift n the positiorrof the slidable bearings 57 and M in the bearing block ifi and 46. In this conne t on, it will be seen that. if. bec use 0 wear. the engagement between the threads 8! on t e worm bearings 5'! and 58, and the slidable hearings ET and 58 snugl fitted into the bearing blocks 45 loosened so' as to permit undesired free movement between the spindle S' and the worm 66, the threads 8-! on the worm- 66 may be positively moved back into firm wedging engagement with the threads 39 on the rack 3i; by rotating the screws 83 and 813 in the proper direction to thereby feed the latter into the bearing blocks- 45 and 46 and push the slidable bearings 5'! and 58 to the left as viewed in Fig. 2.

Thus, it will be seen that with my novel feed adjustment device shown in Figs. 1 to 7, inclu-- sive, the worm 66 may be originally disposed in efficient engagement with the rack 38 on thespindle S by properly adjusting the slidable bearings 51 and 58 in the bearing blocks 55 and 46 and locking the same in these positions by ad justment of the set screws 86 and 67. When so positioned, it will be seen that the Acme threads 8: on the worm- 66 are firmly engaged with corresponding Acme threads 89 on the spindle 8 so that the threads 8i are firmly wedged between the corresponding threads 39 to thereby eliminate backlash therebetween, and are efiec-- tive to hold the spindle against longitudinal movement in the housing H.

justment devices known in the prior art wherein backlash between adjusting device D, worm 66' and the spindle S, which may afiect the proper adjustment. of the spindle S in the bore B, may

be effectively eliminated by properly adjusting the slidable bearings 5? and 553 in the bearings 45 and 46 to eliminate the backlash between the worm 5a and the spindle S, even tho ghbacklash may still remain between the handle Ti and the gear M. This latter is a practical matter of consideration because it will be seen that in constructing a feed ad ustment device in accordance with the princi les of mv invention, with the Acme threads 3 3 and 5H carefully formed, and with the shaft {5% snugly fitted into the s idable and 45, the remaining portions of the feed adjustment device D need not be carefully fitted but may be fitted even outside the usual commercial tolerances without afiecting the efficient operation of my device because it is immaterial how much backlash there is between the handle IT and the gear Hi, this latter backlash having no effect on the backlash between the spindle S and the feed adjustment device D.

have been used on like parts and the same reference numerals with the suffix m have been used on parts which are similar but which have been substituted for parts of the preferred form of my invention.

The changes shown in Fig. 8 over the construction of the device shown in Figs. 1 to '7, are embodied entirely in the adjustment mechanism for adjusting the slidable bearings i and 53 in the bearing blocks i5 and 45. Thus, it will be seen that in Fig. 8, the adjusting screws 83 and 8d and the set screws 863 and 8'! shown in Figs. 1 to 7, have been eliminated and an adjusting screw ii is rotatably mounted in the side wall 25 of the housing H and is secured therein against longitudinal movement therethrough by suitable members such as collars Hi2 and W3. flue head I84 of the screw iiii projects outwardly from the end wall 24 and affords means for rotating the screw. The other end portion of the screw iii! has threads F85 formed thereon which are engaged with threads E66 formed in a slidable bearing 5'im mounted in a bearing block m in the same manner that the slidable bearings 5i and 58 are mounted in the bearing blocks :65 and it. The bearing block dam has a recess iii? formed therein, within which the collar I92 is disposed. The threaded end portion of the screw lEil is journaled in an opening Hit in the bearing block Adm and thus it will be seen that by rotating the screw 552 the slidable bearing 571m may be adjusted in the bearing block the threads E95 on the longitudinally fixed screw it? being effective to move the slidaoie bearing dim toward or away from the wall 2% in accordance with the direction in which the screw lill is rotated.

From the foregoing it will be seen that I have ailorded a novel feed adjustment device which is operable to adjust and support feed mechanism of machine tools and the like in a novel and expeditious manner.

Also it will be seen that I have provided a novel feed adjustment device wherein backlash between the device and mechanism to be adjusted thereby may be efiectively and efficiently eliminated.

In addition, it will be seen that I have afforded a novel feed adjustment device which is practical and efficient in operation and may be economically manufactured.

Thus, while I have illustrated and described preferred embodiments of my invention, it is to b understood that these are capable of variation and modification and I therefore do not wish to be limited to the precise details set forth, but desire to avail myself of such changes and alterations as fall within the purview of the following claims:

I claim:

1.1m a machine tool embodying a housing, andan elongated spindle reciprocably mounted in said housing for longitudinal adjustment therein, a pair of bearings mounted on said housing in spaced relation to each other, a second pair of bearings mounted in said first mentioned bearings, each of said second bearings being movably mounted on a corresponding one of said first mentioned bearings for movement in a predetermined range toward and away from said spindle, a shaft rotatably mounted in said second pair of bearings, a gear mounted on said shaft for rotation therewith, said gear having tapered teeth operatively engaged with said spindle for moving said spindle longitudinally in said housing during rotation of said gear with said shaft, and means for moving said second bearings in said predetermined range of movement on said first mentioned bearings to thereby adjust the position of said shaft relative to said spindle and thereby adjust the operative engagement of said gear teeth with said spindle.

2. In a machine tool embodying a housing, and an elongated spindle reciprocably mounted in said housing for longitudinal adjustment therein, a pair of bearings mounted on said housing in spaced relation to each other, a second pair of bearings mounted on said first mentioned bearings, each of said second bearings being movably mounted on a corresponding one of said first mentioned bearings for movement through an adjusting movement toward and away from said spindle, a shaft rotatably mounted in said second pair of bearings, a gear mounted on said shaft for rotation th rewith between said second bearings, said gear including tapered teeth having oppositely disposed faces disposed at predetermined angles and operatively engaging said spindle for moving said spindle longitudinally in said housing upon rotation of said gear, and means mounted in said first mentioned bearings for moving second hearing in said adjusting movement toward. said spindle to thereby urge said shaft toward said spindle and move said oppositely disposed faces on predetermined ones of said teeth into oppositely camming engagement with said spindle.

3. In a machine tool embodying a housing, and elongated spindle reciprocably mounted in said housing for longitudinal movement therein, a pair of bearings mounted on said housing, a econd pair of bearings, each of said second bearsaid first mentioned bearings, a shaft rotatably mounted in said second pair of bearings, a gear inted on said shaft for rotation therewith, said gear including teeth having oppositely tapered faces, said second bearings being movable on said first mentioned bearings into a predetermined position to thereby move said oppositely tapered faces on predetermined ones of said teeth into oppositely camming operative engagement with said spindle for moving the latter longitudinaily in said housing during rotation of said gear, and means mounted on said first mentioned bearings for releasably retaining said second bearings in said predetermined position.

4. In a machine tool embodying a housing, and an elongated spindle reciprocably mounted in said housing for longitudinal movement therein, a pair of bearings mounted on said housing, each of said bearings having an end disposed adjacent to said spindle and another end disposed on the opposite side of said first mentioned end from said spindle, a second pair of bearings, each of said second bearings being slidably mounted on a corresponding one of said first mentioned bearings for movement toward and away from said spindle, a gear rotatably mounted on said second pair of bearings and supported thereby, said gear being operatively engageable with said spindle for moving the same longitudinally in said housing when said second pair of bearings are disposed in a predetermined position on said first mentioned bearings, and means for moving said second bearings into said predetermined position, said means comprising threaded members mounted in said other ends of said first mentioned bearings and engaged with said second bearings.

5. In a machine tool embodying a housing, and an elongated spindle reciprocably mounted in said housing for longitudinal movement therein, a pair of bearings mounted on said housing, each of said bearings having an end disposed adjacent to said spindle and another end disposed on the opposite side of said first mentioned end from said spindle, a second pair of bearings, each of said second bearings being slidably mounted on a corresponding one of said first mentioned bearings for movement toward and away from said spindle, a gear rotatably mounted on said second pair of bearings and supported thereby, said gear being operatively engageable with said spindle for moving the same longitudinally in said housing when said second pair of bearings are disposed in a predetermined position on said first mentioned bearings, and means for moving said second bearings into said predetermined position, said means comprising elongated threaded members mounted in and threadedly engaged with said other ends of said first mentioned bearings and abutting said second bearings.

6. In a machine tool embodying a housing, and an elongated spindle reciprocably mounted in said housing for longitudinal movement therein, a pair of bearings mounted on said housing, each of said bearings having an end disposed adjacent to said spindle and another end disposed on the opposite side of said first mentioned end from said spindle, a second pair of bearings, each of said second bearings being slidably mounted on a corresponding one of said first mentioned bearings for movement toward and away from said spindle, a gear rotatably mounted on said second pair of bearings and supported thereby, said gear being operatively engageable with said spindle for moving the same longitudinally in said housing when said second pair of bearings are disposed in a predetermined position on said first mentioned bearings, and means for moving said second bearings into said predetermined position, said means comprising elongated members rotatably mounted in said housing and secured therein against longitudinal movement, each of said members being rotatably mounted in a corresponding one of said first mentioned bearings and being threadedly engaged with said second bearing mounted thereon.

7. In a machine tool embodying a housing, and an elongated spindle reciprocably mounted in said housing for longitudinal movement therein, a pair of bearings mounted on said housing, each of said bearings having an end disposed adjacent to said spindle and another end disposed on the opposite side of said first mentioned end from said spindle, a second pair of bearings, each of said second bearings being slidably mounted on a corresponding one of said first mentioned bearings for movement toward and away from said spindle, a gear rotatably mounted on said second pair of bearings and supported thereby, said gear being operatively engageable with said spindle for moving the same longitudinally in said housing when said second pair of bearings are disposed in a predetermined position on said first mentioned bearings, and means for moving said second bearings into said predetermined position, said means comprising elongated embers ro tatably mounted in said housing, collars fixedly mounted on said elongated members on opposite sides of a portion of said housing for holding said elongated members in fixed longitudinal position in said housing, each of said elongated members having one end for rotating said member, and having another end journaied in a corresponding one of said first mentioned bearings, said other end of each of said elongated bearings being threadedly engaged with said second bearing mounted on said corresponding first mentioned bearing for moving said second bearing on said corresponding first mentioned bearing upon rotation of said elongated member in said housing and said first mentioned bearing.

8. In a machine tool embodying a housing, and an elongated spindle reciprocably mounted in said housing for longitudinal adjustment therein, said spindle having a feed rack extending longitudinaliy along one side thereof, said rack comprising threads, a pair of bearing members mounted on said housing in spaced relation to each other, each of said bearings having an elongated opening therein, said openings being disposed in parallel relation to each other, each of said bearings having a slot extending therethrough in communication with, and transversely to, said elongated opening in said bearing, a pair of elongated bearing members mounted in said elongated openings, each of said elongated bearing members being mounted in a corresponding one of said elongated openings in axial alignment with said corresponding first mentioned bearing member, each of said elongated bearing members having a cylindricalshaped opening extending therethrough in alignment with said slot in said corresponding one of said first mentioned bearings, an elongated shaft snugly mounted in said cylindrical-shaped openings for rotation therein, a worm mounted on said shaft between said first mentioned bearings for rotation with said shaft, said worm having threads complementary to, and operatively engaged with said threads on said spindle for moving said spindle longitudinally in said housing upon rotation of said gear, means for rotating said shaft, said elongated bearing members being movable longitudinally in said elongated openings along a predetermined path toward and away from said spindle to thereby move said shaft toward and away from said spindle and adjust the operative engagement of said threads on said gear with said threads on said spindle, and screwmeans mounted in said first mentioned bearings for adjusting the position of said elongated bearings along said predetermined path to thereby adjust the position of said shaft relative to said spindle and thereby adjust the operative engagement of said threads on said gear with said threads on said rack.

RAYMOND C. PALMER.

' REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 106,360 Hamlin Aug. 16, 1870 1,035,340 Fresh Aug. 13, 1912 1,670,413 Kneidl May 22, 1928 1,981,216 Archea Nov. 20, 1934 2,507,555 Berthiez May 16, 1950 

